perhaps this will please travis?

_layouts/default.html

@@ -27,7 +27,7 @@
           {% endif %}
 
           {% unless page.hide_navigation == true %}
-            <a href="{{ site.url }}">Home</a> | <a href="{{site.url}}\another-page.html">Another Page</a>
+            <a href="{{ site.url }}">Home</a> | <a href="{{site.url}}\another-page\">Another Page</a>
           {% endunless %}
         </section>
       </div>

_posts/2020-03-18-a-post.md

@@ -7,7 +7,7 @@ excerpt: Example formatting for this theme! Click me!
 
 Text can be **bold**, _italic_, ~~strikethrough~~ or `keyword`.
 
-[Link to another page]({{site.url}}/another-page.html).
+[Link to another page]({{site.url}}/another-page/).
 
 There should be whitespace between paragraphs.
 

another-page.md

@@ -1,9 +1,10 @@
 ---
 layout: default
+permalink: /another-page/
 ---
 
 ## Welcome to another page
 
 _yay_
 
-[back](./)
+[back](../)